It seems like the amount of stretching force I can bring to bear on the hamstrings is limited by the strength of my lower back. Is that correct?
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Jay BazuziMar 9 '11 at 4:04

@Jay - That's incorrect. In both cases it is using your body weight so bending or stretching your back isn't going to make a diff. In exercise one the strain is placed by raising or lowering your other leg to control the amount of weight. In the second exercise you are using the force of the wall to push against your extended leg.
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xiaohouzi79Mar 9 '11 at 4:18

In the first exercise it looks like he is leaning forward however this could be done with a perfectly straight back (or relaxed) and still get the same benefit. Is is an up and down movement.
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xiaohouzi79Mar 9 '11 at 4:20

I highly recommend a product called IdealStretch. The standing/seated hamstring technique is ok, but at some point you're going to cheat and bend your back. The IdealStretch gives you all the benefits of the partner stretch that Dougman describes, but without needing another person.

I've been using this for a few weeks now and I've gone from only being able to touch my ankles to being able to wrap nearly my entire hand over my toes.

One great thing bout the IdealStretch is it easily allows you to load your hamstrings at both ends. If you don't know what this means, let me elaborate a bit. Your hamstrings are attached at two locations: your hips and your knees. Your hamstrings are stretched when your knee is in extension and your hips are in flexion. If you lock your knee fully extended and then begin to flex your hip, you're going to feel that stretch targeted high on your hamstring where it attaches to your hip. If you do the opposite, flexing your hip first and then extending your knee, you'll feel the stretch target your lower hamstrings where they attach to your hip.

The hamstrings are a two joint muscle, meaning that they cross the hip joint as well as the knee joint. So it helps to do different stretches to isolate:

the upper part of the hamstrings (nearest the ischial tuberosity or buttocks insertion)

the lower part (closest to the knee joint)

Also, the hamstrings are made up of 3 different muscles, basically:

the mid-thigh portion

the medial hamstrings (inner posterior thigh)

the lateral hamstrings (outer posterior thigh)

This video targets stretching each of the above. Notice that he engages his abs to control the spine. He uses his breath, rhythmic, dynamic stretches. Here is another variation with dynamic movements in standing using different planes of motion. See if these help, especially isolating and stretching the upper hamstring.

Also there are the prolonged static stretches as well. This static stretch may be easier for you to isolate your hamstrings from your back than the one in your link. Warm up the muscles first with exercise or heat because you get a better stretch with a warm muscle.

Given that you are so restricted that you can only lift your leg 2' you probably have a neural component to the tightness, meaning that it is not just that the muscle is physically shortened, but that the nerves are also “tense” causing the muscle to “hold” that tight pattern. If that is the case, using PNF - contract relax and/or rhythmic stretches may help you release better.

There are also some physical therapy techniques that you could learn. One is called PRRT that releases reflexes and can be very effective. (Sorry there are no youtube videos. You’ll need to take a partner with you and ask your therapist.)

With your description you may also want to stretch your glutes and hip rotators.
In addition to stretching, you can use a foam roller to self-massage and release the hamstrings.

Partner stretching can be helpful for this. Stand with your back flat against a wall and have a partner lift one of your legs up stretching the hamstring. Hold for a bit, then see if you can go slightly further. This should keep your lower back out of the stretch as long as you don't bend forward off the wall during the stretch.

Squat down with your feet flat on the ground, your back almost swayed in a neutral position, and your elbows on your quads a few inches above your knee. Without changing the position of your hips or arms, slowly straighten your legs at the knee.

What Seems to Help My Hamstrings

5 minutes of running or jump rope or whatever to get your heart rate up

Leg swings to the front, side and back, 3 sets of 10 swings on each direction. Don't bend your lower back.

I then do the band stretching per the video. I generally do a set of Yoga up-dog/down-dogs and some round-backed Good Mornings with a very low weight (this helps my back as well as my hamstrings). Consistency is key: I notice when I skip a day (I get tighter), and I notice when I stretch twice in one day (I make faster progress).

I also do Romanian Deadlifts three times a week as part of my lifting workout. It's important to consider that strengthening the muscle is just as important as stretching it, both to avoid injury and to make the hamstring longer.

What Seems to Shorten and Tighten My Hamstrings

I've found some specific hamstring pitfalls: long car rides, sitting down immediately after running or lifting, sitting instead of using a standing desk at work, sitting with my legs underneath the chair.... Avoiding those has been key for me.

Note: cycling is often found to shorten your hamstrings (making them tighter), instead of improving the situation.